Youth, defined as the period between childhood and adulthood, has numerous synonyms. One of the most commonly used is "adolescence," which refers to the period of physical and emotional transition from childhood to adulthood. Other synonyms include "teenage," "young adulthood," "juvenile," "teen," and "youthful." Some of these terms emphasize the chronological aspect of youth, while others emphasize the qualities of youth, such as energy, vitality, and idealism. It's important to choose the right synonym depending on the context of the sentence or passage, and on the specific qualities of youth that are being emphasized.